Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$44.61	3.844%	$46.3248	$46.32	$46.30	$46.30
Purchase #2	$145.54	13.185%	$164.7294	$164.73	$164.75	$164.70
Purchase #3	$132.25	5.222%	$139.1561	$139.16	$139.15	$139.20
Purchase #4	$184.79	11.570%	$206.1702	$206.17	$206.15	$206.20
Purchase #5	$55.94	12.714%	$63.0522	$63.05	$63.05	$63.10
Purchase #6	$181.89	12.216%	$204.1097	$204.11	$204.10	$204.10
Purchase #7	$105.88	3.814%	$109.9183	$109.92	$109.90	$109.90
7 purchase totals =	$850.90		$933.4607	$933.46	$933.40	$933.50